(1) Field of the Invention
The invention relates to an electrical machine, in particular an electric motor, having a rotor with a laminated core consisting of stacked laminating sheets having tangentially extending slots in each of which at least one permanent magnet is accommodated.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
DE 10 2007 029 719 A1 discloses a common electrical machine in which both tangentially acting and radially acting elastic arms are described for reducing the play between the permanent magnet and the slot in the laminated core. In electrical machines, such play causes increased cogging torque, which is perceptible or may cause increased noise to develop in some applications, such as power steering systems. To facilitate assembly of the permanent magnets, not all of the sheets are equipped with elastic arms, but rather adjoining sheets have a recess at the same position. The known solution has the disadvantage that the elastic arms become bent in the motor's axial direction when the permanent magnets are joined, whereby the sheet edge rubs on the permanent magnet and forms chips. The formation of chips is explained primarily by the fact that the arms to be bent are relatively short, resulting in high bending forces. Furthermore, the elastic arms are sometimes arranged in areas that should have the least possible amount of resistance to the magnetic flux. A change in the geometry to achieve different elasticities would also always affect efficiency. Extending the spring arms would increase the resistance in the magnetic circuit and decrease efficiency. Even with an extension of the spring arms, they would bend during assembly. Furthermore, undesirable chip formation from the sheet edges due to shavings from the permanent magnet must also be expected.